collector extensions and improved ET'S
Had a conversation once with an VERY experienced super stock racer and he said that the perfect collectors would be one's that would fall off in high gear. On most small block cars that don't have as much torque as a big block cars collectors will help make more bottom end torque. The only real way to know what length you need is on a dyno or testing at the track with different lengths to see what your combination likes. JMO